1. Field of the Invention
The present invention is directed to an arrangement for connecting a computer to a digital telecommunications network to exchange data between the computer and other data transmission and data receiving devices connected to the telecommunications network, and to a method for bit rate adaptation of a data channel, over which control data and/or useful data in a data stream are exchanged between at least two units or data networks operating at different transmission rates, in particular between a telecommunications network and a computer, and to the use of the method in the arrangement.
2. Discussion of Background and Other Information
In principle, Integrated Services Digital Network (ISDN) provides two different modes of subscriber access: basic access and primary rate access. The primary rate access can be subdivided into what are known as channel structures. A distinction is made between an H1, an H0, and a B channel structure and a mixed structure. In the mixed structure, a combination of B and H0 channels can be chosen. While the transmitted data of the various B, H0 and H1 channels are of no significance for handling information over the telecommunications network (this is known as bit-transparent transmission), a signaling channel (D channel) is needed to make and break connections within the telecommunications network. When ISDN subscribers are connected to computer systems, the point of departure thus far has been basic access, or at best, primary rate access with an H1 channel structure. The basic access mode, which allows a maximum transmission rate of 144 kbit/s, can be achieved with a relatively modest expenditure for circuitry per access unit. However, its disadvantage is the low number of subscriber connections per access unit, because basic access provides only two B channels and one D channel. If 30 simultaneous subscriber connections are needed, for example, then 15 access units must be made available. This high expenditure for circuitry on the one hand increases the costs and the effort and expense for service, and it also lowers the reliability of the overall system. Although primary rate access with an H1 channel structure does allow the planned transmission rate of 2 Mbit/s, it is usable only for communication between two ISDN subscribers; that is, the transmission in the telecommunications network is bit-transparent over the entire channel bandwidth of the primary rate access. For an interface component unit for processing a primary access with a B channel structure, which according to CCITT I-431 furnishes the user with 30 B channels (basic channels) and one D channel (auxiliary channel) at 64 kbit/s, and thus allows 30 different subscribers to have simultaneous access to one computer, an interface subassembly for processing a primary rate access with an H1 channel structure cannot be used.